The commercial production of a variety of desirable metabolites and important pharmaceuticals can employ the overexpression capacity of oxygen-requiring bacteria, fungi and mammalian cells. Further, during the optimization of a process (e.g., fermentation) for producing a commercial product involving a facultative aerobe or a product pathway that requires oxygen, oxygen delivery to the microbe often becomes rate limiting. This can largely be due to the incredibly low surface area to volume ratio of industrial scale processes (e.g., fermentations). Oxygen has very low solubility in water and various microorganisms and cultured cell types have high nutritional demand for oxygen, especially during large-scale and high-cell-density production processes. The high demand for oxygen can be partially satisfied by improving process parameters and bioreactor configurations, e.g. improved mixing rates, high-efficiency dispersion systems and modifications of the medium, which can all serve to increase the partial pressure of oxygen in the production medium. However, these improvements often directly contribute to the capital and operating cost of running the production process. Further, such improvements often employ methods that can produce undesirable rheological properties such as turbulence and/or shear rates in the culture vessel as well as utilize culture media that may produce suboptimal growth rates for a desired host microoganism.
Thus, there is a great need in the art for creative solutions to the problem of oxygen limitation in industrial fermentations, which are widely applicable to a range of microorganisms and are not dependent upon optimizing physical bioreactor components or fermentation media.